Wiring grille and method of making the same



Aug. 18, 1936.

WIRING GRILLE AND METHOD OF MAKING THE SAME Filed Sept. 19, 1935 F121. 1 oooo oooocfcooeoo I E. H. KALMBACKER 2, 5 ,639

Fig. 2. 1-1;. 5.

In venoor:

Edward H. Kalmbacker,

Patented Aug. 18, 1936 WIRING GRILIE AND METHOD or MAKING THE SAME Edward H. Kalmbacker, Collingdale, Pa., assignor to General Electric Company, a corporation of New York Application September 19, 1935, Serial No. 41,251

7 Claims,

For certain kinds of electrical work, it is important to have a means capable of supporting a large number of insulated current carrying wires, which may be readily attached to and removed from some fixed structure or support. An

example of a means for such purposes is found in the patent to Reed and Paxton, No. 2,006,150 issued June 25, 1935, therein referred to as a perforated wiring strip and through which insulated wires extend. For reasons of economy of manufacture and reduction in size, it is desidable to make the wiring strip or grille out of thin metal, such as sheet steel. To provide a grille suitable for a large number of wires means that it must have a correspondingly large number of openings or perforations to receive the circuit wires. Because the number and arrangement of the wires on one panelboard or'equivalent device may differ from those of another and because for manufacturing reasons the grilles should be made in quantities from the same set of dies, they are provided with a much larger number of holes or perforations than are commonly necessary for any particular piece of work. To save space in or on the structure using the grille and also to save stock in the grille itself, the openings or perforations, which are small in diameter, are made as close together as possible, leaving only such an amount or section of metal between holes as will aiford a suitable support. To simplify the wiring as a whole, each wire depends upon its own insulation as protection from ground and short circuits. It is a simple matter, of course, to punch with an ordinary punchand die a lot of spaced holes in a strip of metal but in so doing a small burr will be left in many, if not all, cases on the side of the strip through which the punch protrudes on its working stroke. These burrs are liable to injure the insulation on the wires, p ticularly if the same portion of a wire is pulled through two burred openings in succession, and hence are a potential source of danger. Even if the burrs are removed, there still remains the danger of injuring the insulation due to the relatively sharp edge of the thin wall of the opening.

An object of my invention is the provision of an improved metal grille for wire supporting purposes wherein the walls of the perforations are so rounded or curved on both sides of the grille that insulation on the wires supported thereby is amply protected against cutting or other injury as the wires are pulled into place.

A further object of my invention is an improved.

method of making wiring grilles of thin metal and specifically in the method of forming the walls of the perforations therein so that ,the ends thereof will present smooth curved unbroken surfaces on both sides of the grille.

For a consideration of what I believe to be novel and my invention, attention is directed to the accompanying description and the claims appended thereto.

In the accompanying drawing, which is illustrative of my invention, Fig. 1 is a plan view of my improved wiring strip; Fig. 2 shows on a greatly enlarged scale the die means for performing the first operation in the formation of the holes or perforations in the wiring strip; Fig. 3 the die means for the second operation, and Fig. 4 the .die means for the final or curling operation.

Numeral 5 indicates the wiring strip or grille which is made of thin sheet steel. As an example, it maybe made of No. 16 gauge steel having a thicknessof approximately .065 of an inch.

It is provided with a large number of perforations or openings 6, arranged in rows and with only enough metal between them to properly define the walls. It has been found by arranging or spacing the openings in parallel rows as shown that the largest number for a given surface area may be made. Shduld the requirements for the grille be less exacting, a greater pitch distance or spacing between openings may be employed. In other words, a greater amount of stock between openings may be provided.

It will be seen that the amount of metal between the walls of any two adjacent openings is very small and therein lies one of the chief dimculties of manufacture. Because of the thinness of the stock of which the grille is composed and because the amount of metal between two adjacent openings is so small, it is impractical to punch the openings and at the same time draw the metal of the sheet stock to any substantial extent around each opening from which to form a well rounded exit. The metal disk which results from cutting the metal to form each opening and which ordinarily would be waste material in its entirety is in my construction partially utilized. The small saving in metal is, of course, not material, the important fact is that without utilizing the waste material as disclosed herein, the desired formationof the exit wall of the opening on the back of the grille would not be attained. Briefly stated, I utilize a portion of the metal of the disk from each opening toi'orm a flange on the back side of the grille which is subsequently curled outwardly from the axis of the opening to form a smooth curved surface over which a wire may be pulled without injury to its insulation.

A portion of the disk sufficient to form a suitable small flange on the back side of the grille is obtained by the use of suitable dies such as is shown in Fig. 2, wherein 5 indicates the stock of which the grille is composed on a greatly enlarged scale. Numeral 8 indicates the body of the die, the wall of which is slightly tapered outwardly at its upper end as indicated at 9 to afford a small additional space for metal when subjected to heavy pressure. The upper corner of the die is also slightly rounded to prevent injury to the stock as the punch-descends. Inside of the die and forming a part thereof is an insert l0 having a crowned top surface I I. Numeral I2 indicates a drawing punch having a projection 13 on its under side of a depth somewhat greater than the thickness of the stock of the grille. Between the upper end of the projection and the body of the punch is a fillet M of such radius as to form a smooth curved surface on the grille at the entrance of the wire receiving opening. It will be noted that the punch does not pass entirely through the stock. Because of that fact and because of the crowned upper face H of the insert where the pressure is highest, metal is caused by the heavy pressure exerted thereon to flow radially from the center toward slightly tapering wall 9 of the die and in so doing fill the entire space between the punch and die except for the small annular space indicated at l5. The effect of this operation is to form a shallow inset H5 in the grille as viewed from the top surface thereof in Fig.2, said inset having an annular wall of substantial thickness but one which is less than that of the stock itself. The depth of the inset is greater than the thickness of the sheet stock, the purpose being to provide material for a flange on the back side of the stock as will appear later. Having properly formed the inset, the next step is to punch out the small disk situated within the annular wall. This is done by a piercing punch H and a. piercing die It as shown in Fig. 3. The result of this operation is to remove the small center part or disk and leave an annular flange l9 of substantial radial thickness, and one having a uniform and sufidcient depth. By forming the flange in the manner described, it will hnoted that the section of metal between openings or perforations has not been disturbed.

After the flange is formed, the stock ready for the third operation which consists in curling the flange so that it will present a smooth curved surface to the entering circuit wire. This is done by a curling punch. to having an upi tending projection 2i and. a well IGl at the bottom .ereof. In this case,

' of the grille by tl one metal of the flan 22 which cause as the pressure As the net 1' scribed, the v. the grille is e opening or p ded on both grille and no s or projec" to cut or injure .e insulation wires as they book the grille.

For simplicity, described with foration. In pra forations should be like manner. satisfactory to c as twenty-eight, 2

other structure.

In many cases, it is desirable to support various' wiring devices on the grille instead of securing them to the back of the panelboard. For this purpose, one edge, say the upper edge, of the grille has a row of holes 24 which are adapted to receive clamping screws. The holes are closely spaced and. their pitch distance bears no exact relation to the parts to be supported thereon. The main consideration is to have holes so closely spaced and extending for a sufficient portion of the length of the grille as to permit securing in place of various wiring devices.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. As an article of manufacture, a wire support comprising relatively thin elongated sheet metal stock having a series of openings therein each of which has an inwardly curved entrance wall and an outwardly curled flange integral with the stock on the back side thereof and of larger diameter than the opening, said flange projecting from the back wall of the stock and defining an outwardly curved exit for the open- 2. As an article of manufacture, a wire supporting grille comprising a strip of thin metal having numerous openings to receive insulated Wires, the wall at the entrance of each opening being curved on a small radius and the wall at the exit of each opening being formed by a thickened and outwardly curved portion of the stock of the strip.

3. As an article of manufacture, a wire supporting grille comprising a strip of thin sheet metal having a large number of openings arranged in rows with narrow walls between them, the entrance wall of each opening being curved and the exit wall thereof formed as an integral outwardly curled portion of the metal of which the strip is composed.

4. As an article of manufacture, a wire supporting grille comprising a thin flat strip of metal having a large number of closely spaced wire receiving openings, each of said openings having a curved entrance wall and a thickened outwardly curved exit wall, openings along one edge of the grille to receive supporting means therefor, and a row of closely spaced openings on the opposite edge forming means to receive sup ports for devices to be carried by the grille.

5. The method of making a wire support from sheet metal which comprises forming an inset therein with a curved entrance wall, the depth of the inset being greater than the thickness of sheet stock, removing the disk of metal defined by the inner wall of the inset to form an flange, and curling the flange outwardly '"'s of the opening to form a smooth surface therefor. method of making wire supporting a large number of closely space ing openings which comprises iii forming an inset with a curved entrance for each opening, removing the disk of metal defined by the inner wall of the inset to form an annular flange, and curling the flange away from the axis of the opening to form a smooth rounded surface therefor.

7. The method of making wire supporting grilles having a large number of spaced wire receiving openings with narrow walls between them which comprises forming an inset with a curved entrance for each opening, causing metal to flow radially outward from the center of the inset partly to form the side wall thereof, removing the disk'of metal defined by the side wall of the inset to form a flange, and curling theflange away from the axis of the opening to form a smooth rounded surface therefor.

EDWARD H. KALMBACKER. 

